SWIFT

Swift Computed Property

class Calculator {

  // define stored property
  var num1: Int = 0
  ... 
}

Swift Computed Property In Extension

extension Circle {
  // stored property
  var radius: Int // error code
}

Computed Property In Extension Swift

class Circle {
  var radius: Double = 0
}

extension Circle {
  // define computed property 
  var area: Double {
    return 3.14 * radius * radius
  }
}

let circle1 = Circle()
circle1.radius = 5
print("Area:", circle1.area)